If you are buying a new bike, I recommend going with the manufacturer's suggested size for that model bike. Some actually do have different sizing recommendations for various models. I'd even apply the same to an old bike if you can find the recommendations.

If a manufacturers size recommendation is between two size bikes, then generally, the smaller frame will feel more sporty and you might actually make more power on it. The larger frame will feel more stable at speed and depending on your specific body dimensions might be more comfortable, but could be less comfortable if your dimensions go the other way.

If you want to run calculators and stuff on the web that supposedly pick the perfect frame size for you, then you really are obsessing too much about your perfect pick for a bike. Hopefully it's your first road bike. Not your last road bike. As you get experience, you'll realize things you want different in your next bike if you pay attention.